Green ophthalmic glass



l a-38 SF? United States Patent GREEN OPHTHALMIC GLASS William H.Armistead, Corning, N. Y., assignor to Cormng Glass Works, Coming, N.Y., a corporation of New York No Drawing. Application February 18, 1952,Serial No. 272,244

11 Claims. (Cl. 106-53) This invention relates generally to greenglasses and is particularly concerned with imparting a greenish color tolead-containing glasses such as the flint glasses used lfor thehigh-index segments of multifocal ophthalmic enses.

Green eye-protecting spectacles or sun glasses are commonly composed ofgreen spectacle crown glass, the green coloration of which is producedby a mixture of FeO and F6203 resulting from introducing into its batchan iron oxide and melting the batch under reducing conditions. The colorof such glass has become standardized and the glass is conventionallyproduced in four different shades (2 mm. thickness) designated A, B, Cand D and ranging in color saturation from light to dark greenrespectively (National Bureau of Standards Circular No. 471 issuedOctober 8, 1948). Green spectacle crown glass is normally softer thanstandard white optical crown glass, however, because, with theintroduction of iron oxide thereinto, it is necessary to decrease thenormal CaO content of the base glass in order to maintain the desiredrefractive index, thereby substantially lowering the softening point.

When green spectacle crown glass is utilized for making multifocalophthalmic lenses, it is desirable that the high-index segments thereofbe composed of a flint glass because, generally speaking, flint glassesnot only have the requisite high refractive indices but also have thedesirably lower softening points which are necessary in order to avoiddistortion of the crown glass when the former. are sealed thereto. Forsuch use it is also desirable that the flint glass have a color exactlyor substantially exactly matching that of the green spectacle crown. Sofar as applicant is aware, however, the production of the desired colorin a flint glass has not heretofore been accomplished. Attempts to colora flint glass with FeO. for example, have been unsuccessful becausemelting of glasses containing substantial amounts of PhD (3% or more)under the reducing conditions necessary to pro- 2,699,399 Patented 'Jan.11, 1955 ice the oxides of antimony, chromium, nickel and cobalt incertain proportions, together with an oxidizing agent such as an alkalimetal nitrate. Moreover, the present discovery is also applicable to theproduction of a greenish color in silicate glasses in general.

While substantially any oxidized silicate glass may be so colored, thepractical range of compositions encompassed by this invention comprisesessentially 33 to $102, at least one alkali metal oxide in the indicatedproportion selected from the group consisting of up to 12% K20, up to15% NazO and up to 4% LizO, the selected alkali metal oxide including anoxide selected from the group consisting of K20 and NazO, the total ofthe alkali metal oxides being 5 to 15%, at least one bivalent metaloxide in the indicated proportion selected from the group consisting ofup to 5% Eco, up to 10% MgO, up to 15% CaO, up to 15% ZnO, up to 15%SrO, up to 15% CdO, up to 35% 3:30, and up to PbO, the selected bivalentmetal oxide including an oxide selected from the group consisting ofCaO, ZnO, BaO and PbO, the total of the bivalent metal oxides being 15to 60%, 0.1 to 20% SbzOs, 0.02 to 0.8% CrzOs, 0.01 to 0.25% MO and 0.001to 0.025% C00, the total of the essential constituents being at leastEach of the four oxides SbzOs, CrzOs, NiO and C00 is essential for theproduction of the desired color and must be present in the glass in theabove proportions. $1520: per se does not color glass and amountsexceeding 1% have no additional efiect on the color of the presentglasses although amounts up to 20% may, if desired, be utilized as anadditional glass-making oxide. T 0 produce the desired hues, the amountof CrzOs should be from 1.5 to 5 times the amount of NiO and the amountof NiO should be from 3 to 20 times the amount of C00.

Other metal oxides which may be present in limited amounts in theglasses of this invention include B203 in amounts up to 8%, butpreferably not over 5%, A1203 in amounts up to 5%, TiOz in amounts up to12%, and ZrOz in amounts up to 15% except in ead glasses free of otherbivalent metal oxides in which case not more than about 7% of 2102 willdissolve in the glass. Such optional metal oxides should not total morethan 25%.

The following glass compositions calculated from their respectivebatches to the oxide basis in parts by weight will illustrate theinvention. The amounts of the coloring oxides Cr2O3, NiO and C00, beingless than one, are necessarily expressed in three to four significantplaces; but such practice is without significance in expressing themajor constituents. Since each composition totals approximately theamounts given for the various constituents thereof can for practicalpurposes be called per cent by weight.)

Color (Shade) 13 C B D duce the iron oxide greenish tintresults in thereduction of the PbO to metallic lead and in an undesirablediscoloration of the glass thereby.

I have now discovered that ophthalmic flint glasses.

in particular can be colored, without resort to reducing The aboveglasses are melted under oxidizing conditions by including in theirbatches an alkali metal nitrate.

The colors of the resulting glasses are similar-in .ap.- pearance to thecolors produced by a mixture of FeO.

and FezOs in green, crown glasses melted under reducing agents, to asuitably close match for green spectacle 30 conditions. The glasses ofexamples 1 to 7 are fiints,

crownglass'by including in their batches a-mixture ofexamples2 and]being bariumilints. Theglasses of.

sca 1 examples 1 to 4 are particularly suitable in color, softeningpoint and refractive index for combination as bifocal buttons with greenspectacle crown glasses. While the invention is especially adapted forthe production of such green-colored lead-containing ophthalmic glasses,it may also advantageously be utilized for the green coloration ofsilicate glasses in general, such as, the non-lead glasses of examples 8and 9.

Variations in the proportions of the essential coloring constituents ofthe glasses of this invention should be confined within the limits setforth above for the following reasons:

From the standpoint of coloration Sb202 functions to make the color dueto Cr2O3 more green or less yellow by increasing the transmission ofblue wave lengths thereby. A deficiency of SbzOg therefore results inthe color of the glass being too yellowish. More the: i She-1".- resultsin an objectionable tendency of the glass to devitrify.

From this it follows that an excess of CrzOs will increase the greentransmission or brighten the green appearance of the glass too much. Onthe other hand, a deficiency of Cr203 will cause the color of the glassto tend too much towards gray.

In combination the NiO and C provide a neutral or gray tint for thepurpose of dulling or reducing the brightness of the green color due toCr202. Too much NiO or too little C00 will make the color too yellowwhile too much C00 or too little NiO Will make the color too blue. Withthe NiO and C00 in the proper ratio an excess of both will cause theglass to appear too gray but a deficiency of both will cause the greencolor of the glass to appear too bright.

It is characteristic of the present glasses that, when the percentage ofeach of the oxides, Sb203, CrzOs, NiO and C00 which produces the desiredhue has once been determined, any desired shade may thereafter beobtained by merely varying the percentages of CrzOs, NiO and C00 withoutchanging their respective ratios with one another.

The remaining essential constituents of the present glasses have nosubstantial effect upon their color, but o her phvsical and chemicalproperties of the glass are affected thereby as follows:

The softening point is objectionably increased by an excess of eitherSiOz, BeO, or CaO and is decreased by an excess of the alkali metaloxides. The acid durability of the glass becomes undesirably low with adeficiency of SiOz or an excess of alkali metal oxide, MgO, SrO, CdO, orPbO. Devitrification of the glass results from an excess of MgO, CaO,ZnO, or BaO. The maintenance of the desired refractive index requiresthat the total bivalent metal oxides be between 15 and 60%.

0f the non-essential constituents, A1203 in excessive amounts causes anobjectionable increase in the softening point of the glass and anundesirable decrea acid durability. An excess of H203 also lows.durability, while an excess of ZrOz or TiOz incrca. tendency for theglass to devitrify.

As used herein, the softening point of a glass is that temperature atwhich the glass has a viscosity in the neighborhood of 4.5)(10 poises.

What is claimed is:

1. A glass composition comprising essentially by weight 33 to 55% Si02,at least one alkali metal oxide in the indicated proportion selectedfrom the group consisting of up to 12% K20, up to 15% NazO and up to 4%Li20, the selected alkali metal oxide including an oxide selected fromthe group consisting of K20 and Na2O, the total of the alkali metaloxides being to 15%, at least one bivalent metal oxide in the indicatedproportion selected from the group consisting of up to 5% BeO, up toMgO, up to CaO, up to 15% ZnO, up to 15% SrO, up to 15% CdO, up to 35%BaO and up to 60% PbO, the selected bivalent metal oxide including anoxide selected from the group consisting of CaO, ZnO, BaO and PbO, thetotal, of the bivalent metal oxides being 15 to 60%, 0.1 to SbzOs, 0.02to 0.8% Cr203, 0.01 to 0.25% NiO and 0.001 to 0.025% C00, the ratioCrzOa/NiO being from 1.5/1 to 5/1 and the ratioNiO/CoO being from 3/1 to20/ 1, the total of the essential constituents being at least 75%.

2. A glass composition comprising essentially by weight 33 to 55% Si02,at least one alkali metal oxide in the indicated proportion selectedfrom the group consisting of up to 12% K20, up to 15% Na20 and up to 4%Li20, the selected alkali metal oxide including an oxide selected fromthe group consisting of K20 and Na20, the total of the alkali metaloxides being 5 to 15%, 15 to 60% PbO, 0.1 to 20% SbzOs, 0.02 to 0.8%Cr203, 0.01 to 0.25% NiO and 0.001 to 0.025% C00, the ratio CrzOs/NiObeing from 1.5/1 to 5/1 and the ratio NiO/CoO being from 3/1 to 20/ 1,the total of the essential constituents being at least 75 3. A glasscomposition comprising essentially by Weight 33 to SiOz, at least onealkali metal oxide in the indicated proportion selected from the groupconsisting of up to 12% K20, up to 15% Na20 and up to 4% LizO, theselected alkali metal oxide including an oxide selected from the groupconsisting of K20 and Na20, the total of the alkali metal 0. ides being254;, Up 11. if, f). 1 11 4 E0. the to 5;- and PbO being 15 to 0.1 to20% SbzOs, 0.02 to 0.8% CrzOs, 0.01 to 0.25% NiO and 0.001 to 0.025%C00, the ratio Cr20s/Ni0 being from 1.5/1 to 5/1 and the ratio NiO/CoObeing from 3/1 to 20/ 1, the total of the essential constituents beingat least 4. A glass composition comprising essentially by weight 33 to55% SiOz, at least one alkali metal oxide in the indicated proportionselected from the group consisting of up to 12% K20, up to 15% NazO andup to 4% Li2O, the selected alkali metal oxide including an oxideselected from the group consisting of K20 and Na20, the total of thealkali metal oxides being 5 to 15%, 15 to 60% PbO, 0.1 to 20% Sb203,0.02 to 0.8% Cr203, 0.01 .o 0.25% NiO 0.001 to 0.025% C00, the ratioCrzOs/NiO being from 1.5/1 to 5/1 and the ratio NiO/CoO being from 3/1to 20/ 1, the total of the essential constituents being at least 75%,and up to 5% A1203.

5. A glass composition comprising essentially by weight 33 to 55% SiOz,at least one alkali metal oxide in the indicated proportion selectedfrom the group consisting of up to 12% K20, up to 15% Na20 and up to 4%LizO, the selected alkali metal oxide including an oxide selected fromthe group consisting of K20 and Na20, the total of the alkali metaloxides being 5 to 15%, 15 to 60% PbO, 0.1 to 20% SbzOs, 0.02 to 0.8%Cr203, 0.01 to 0.25% NiO, 0.001 to 0.025% C00, the ratio Cr20s/Ni0 beingfrom 1.5/1 to 5/1 and the ratio Ni0/Co0 being from 3/1 to 20/ 1, thetotal of the esslergial constituents being at least 75 and up to 12% 6.A glass composition comprising essentially by weight 33 to 55% SiOz, atleast one alkali metal oxide in the indicated proportion selected fromthe group consisting of up to 12% K20, up to 15% NazO and up to 4% LizO,the selected alkali metal oxide including an oxide selected from thegroup consisting of K20 and NazO, the total of the alkali metal oxidesbeing 5 to 15%, 15 to 60% PbO, 0.1 to 20% 513202. 0.02 to 0.8% CrzOz,0.01 to 0.25% NiO, 0.001 to 0.025% C00, the ratio CrzOs/NiO being from3.5/2 15 5/1 and the ratio NiO/CoO being from 3/ 1 to 20/1, the total ofthe essential constituents being at least 75 and up to 7% ZrO2.

7. A glass composition comprising essentially by weight 33 to 55% Si02,at least one alkali metal oxide in the indicated proportion selectedfrom the group consisting of up to 12% K20, up to 15% NazO and up to 4%Li20, the selected alkali metal oxide including an oxide selected fromthe group consisting of K20 and NazO, the total of the alkali metaloxides being 5 to 15%, up to 35% BaO, up to 60% PbO, the total BaO andPhD being 15 to 60%, 0.1 to 20% Sb203, 0.02 to 0.8% CrzOa, 0.01 to 0.25%NiO, 0.001 to 0.025% C00, the ratio CrzOs/NiO being from 1.5/1 to 5/1and the ratio NiO/CoO being from 3/1 to 20/1, the total of the essentialconstituents being at least 75 and up to 8% B203.

8. A glass composition comprising essentially by weight 33 to 55 SiOz,at least one alkali metal oxide in the indicated proportion selectedfrom the group consisting of up to 12% K20, up to 15% NazO and up to 4%Li20, the selected alkali metal oxide including an oxide selected fromthe group consisting of K20 and NazO, the total of the alkali metaloxides being 5 to 15%, up to 35% BaO, up to 60% PbO, the total BaO andPhD being 15 to 60%, 0.1 to 20% SbzOs, 0.02 to 0.8% CrzOs, 0.01 to 0.25%NiO, 0.001 to 0.025% C00, the ratio CrzOs/NiO being from 1.5/1 to 5/1and the ratio Ni0/Co0 being from 3] to ZQ/I, the total of the essentialconstituents being at least 75%, and up to 12% TiOz.

Q. A glass composition comprising essentially by weight 33 to 55% SiOz,at least one alkali metal oxide in the indicated proportion selectedfrom the group consisting of up to 12% K20, up to 15 NazO and up to 4%LizO, the selected alkali metal oxide including an oxide selected fromthe group consisting of K20 and NazO, the total of the alkali metaloxides being to up to 35% BaO, up to 60% PbO, the total BaO and PbObeing 15 to 60%, 0.1 to 513203, 0.02 to 0.8% CrzOa, 0.01 to 0.25% NiO,0.001 to 0.025% C00, the ratio CrzOs/NiO being from 1.5/1 to 5/1 and theratio NiO/CoO being from 3/1 to 20/ 1, the total of the esaerrgialconstituents being at least 75 and up to 15% 10. A glass compositioncomprising essentially by Weight 33.to 55 SiO2, at least one alkalimetal oxide in the indicated proportion selected from the groupconsisting of up to 12% K20, up to 15% N320 and up to 4% LizO, theselected alkali metal oxide including an oxide selected from the groupconsisting of K20 and NazO, the total of the alkali metal oxides being 5to 15%, 15 to 60% PbO, 0.1 to 20% SbzOz, 0.02 to 0.8% CrzOs, 0.01 to0.25% NiO, 0.001 to 0.025% C00, the ratio CrzOz/NiO being from 1.5/1 to5/1 and the ratio NiO/CoO being from 3/1 to 20/1, the total of theesseigial constituents being at least 75%, and up to 8% 11. A glasscomposition comprising essentially by weight 33 to SiO2, at least onealkali metal oxide in the indicated proportion selected from the groupconsisting of up to 12% K20, up to 15% NazO and up to 4% LizO, theselected alkali metal oxide including an oxide selected from the groupconsisting of K20 and NazO, the total of the alkali metal oxides being 5to 15%, up to 35% BaO, up to PhD, the total BaO and PbO being 15 to 60%,0.1 to 20% 517203, 0.02 to 0.8% CrzOa, 0.01 to 0.25% NiO, 0.001 to0.025% CoO, the ratio CrzOs/NiO being from 1.5/1 to 5/1 and the ratioNiO/CoO being from 3/1 to 20/ 1, the total of the 6SS6H1211 constituentsbeing at least and up to 5% A12 3.

Rx Lenses, American Optical Company Catalog, page 64, published in 1950.

1. A GLASS COMPOSITION COMPRISING ESSENTIALLY BY WEIGHT 33 TO 55% SIO2,AT LEAST ONE ALKALI METAL OXIDE IN THE INDICATED PROPORTION SELECTEDFROM THE GROUP CONSISTING OF UP TO 12% K2O, UP TO 15% NA2O AND UP TO 4%LI2O, THE SELECTED ALKALI METAL OXIDE INCLUDING AN OXIDE SELECTED FROMTHE GROUP CONSISTING OF K2O AND NA2O, THE TOTAL OF THE ALKALI METALOXIDES BEING 5 TO 15%, AT LEAST ONE BIVALENT METAL OXIDE IN THEINDICATED PROPORTION SELECTED FROM THE GROUP CONSISTING OF UP TO 5% BEO,UP TO 10% MGO, UP TO 15% CAO, UP TO 15% ZNO, UP TO 15% SRO, UP TO 15%CDO, UP TO 35% BAO AND UP TO 60% PBO, THE SELECTED BIVALENT METAL OXIDEINCLUDING AN OXIDE SELECTED FROM THE GROUP CONSISTING OF CAO, ZNO, BAOAND PBO, THE TOTAL OF THE BIVALENT METAL OXIDES BEING 15 TO 60%, 0.1 TO20% SB2O3, 0.02 TO 0.8% CR2O3, 0.01 TO 0.25% NIO AND 0.001 TO 0.025%COO, THE RATIO CR2O3/NIO BEING FROM 1.5/1 TO 5/1 AND THE RATIO NIO/COOBEING FROM 3/1 TO 20/1, THE TOTAL OF THE ESSENTIAL CONSTITUENTS BEING ATLEAST 75%.